2016-12-09T17:22:17ZVisualising attribute and spatial uncertainty in choropleth maps using hierarchical spatial data modelshttp://hdl.handle.net/10523/1470
Visualising attribute and spatial uncertainty in choropleth maps using hierarchical spatial data models
2005-12
Kardos, Julian
This thesis defines a novel and intuitive method to visually represent attribute uncertainty, and spatial boundary uncertainty generated from choropleth maps. Like all data, it is not possible to know exactly how far from the truth spatial data used for choropleth mapping When spatial data is used in a decision-making context a visual representation of data correctness may become a valuable addition. As an example, the visualisation of uncertainty is illustrated using choropleth mapping techniques superimposed on New Zealand 2001 census data, but other spatial datasets could have been employed. Both attribute and spatial uncertainty are considered, with Monte Carlo statistical simulations being used to model attribute uncertainty.
A visualisation technique to manage certain choropleth spatial boundary issues (i.e. the modifiable areal unit problem — MAUP) and uncertainty in attribute data is introduced, especially catering for attribute and choropleth spatial boundary uncertainty simultaneously. The new uncertainty visualisation method uses the quadtree spatial data model (SDM) in a novel manner. It is shown that by adapting the quadtree SDM to divide according to uncertainty levels possessed by attributes (associated with areal units), rather than divide on the basis of homogeneous regions (as the original quadtree design was intended), a measure of attribute and choropleth spatial boundary uncertainty can be exhibited. The variable cell size of the structure expresses uncertainty, with larger cell size indicating large uncertainty, and vice versa. The new quadtree SDM was termed the trustree. A software suite called TRUST v1.0 (The Representation of Uncertainty using Scale-unspecific Tessellations) was developed to create square trustree visualisations.
The visual appeal and representational accuracy of the trustree was investigated.
Representative accuracy and visual appeal increased when using hexagonal tessellations instead of the quadtree's traditional square tessellation. In particular, the Hexagonal or Rhombus (HoR) quadtree designed by Bell et al. (1989) was used to programme TRUST v1.1. Using the HoR quadtree in rhombic mode (TRUST v1.1.1) produced Orbison's optical illusion, so it was disregarded. However, the HoR trustree (the hexagonal tessellation produced by TRUST v1.1.2) was adopted for further research and user assessment. When assessed using an Internet survey, the HoR trustree adequately displayed choropleth spatial boundary uncertainty, but not attribute uncertainty. New trustree visualisations, the value-by-area (VBA) trustree and adjacent HoR trustree were developed to help increase the expression of attribute uncertainty. Upon reassessment, the new trustree visualisations were deemed usable to express attribute uncertainty and choropleth spatial boundary uncertainty at a modest 58% usable (HoR trustree), 80% usable (VBA trustree) and 85% usable (adjacent HoR trustree). A usability test (where participants were asked to spot different levels of uncertainty) validated these results, whereby the HoR trustree achieved a 65% accuracy level and the VBA trustree achieved an 80% accuracy level.
The user assessments helped to highlight that the trustree could be used in two ways, to express detail within or clutter over areal units. The HoR trustree showed (1) a level of detail (or resolution) metaphor, where more detail represented more accuracy and/or the reverse, (2) a metaphor of clutter, where the data structure output was sufficiently dense as to cover spatial information, in effect hiding uncertain areas.
Further Internet survey testing showed the trustree tessellation works better when representing a metaphor of detail. Attribute and spatial uncertainty can be effectively expressed depending on the tessellation level used.
Overall, the new TRUST suite visualisations compare favourably with existing uncertainty visualisation techniques. Some uncertainty visualisation methods consistently performed better than the TRUST visualisations such as blinking areas, adjacent value and non-continuous cartograms. Other methods like colour saturation, image sharpness and a three-dimensional surface frequently performed with less usability. Therefore, the TRUST visualisations have found their place amongst other uncertainty visualisation methods. However, survey results showed that TRUST is a viable option for visualising two forms of uncertainty — attribute and spatial uncertainty. No other visualisation method has these capabilities. Further research could include a laboratory assessment of TRUST and also incorporating vagueness and temporal uncertainty concepts. Additionally, end-user testing could provide a valuable insight into uncertainty visualisation for everyday use. Adopting uncertainty methods to uncertainty, such as the technique presented here, into the mainstream decision making environment could be considered a fundamental objective for future investigation in spatial studies.
2011-04-07T03:16:49ZSpatial information systems for wildlife conservation management: Taiaroa Head royal albatross colonyhttp://hdl.handle.net/10523/1276
Spatial information systems for wildlife conservation management: Taiaroa Head royal albatross colony
1998-09
McLennan, Bruce
The breeding colony of Northern royal albatross (Diomedea sanfordi) at Taiaroa Head is the only mainland breeding colony of any albatross species. Although it represents only a small proportion of the total population of the species, the ease of access to the colony has led to it becoming an important scientific and tourist resource. Breeding records for the colony date back more than 60 years, and since 1968 daily observation records have been collected. The purpose of this thesis is to present a design for a spatial information system (SIS) for the collection and management of breeding and environmental data, and demonstrate the advantages of such a system. This design is implemented in the form of a prototype SIS for evaluation purposes. What sets this research apart from other studies that have used geographic information system (GIS) software to assist wildlife management is the amount and complexity of data and the time span over which it has been collected. It is proposed that for these data to have maximum utility for wildlife managers at Taiaroa Head, established structured system design and development methodologies are required to ensure data are efficiently stored and important relationships between data are retained.
Three experiments are carried out to evaluate the prototype SIS and demonstrate the range of analyses that are possible. The first experiment inductively explores the spatial relationship between nest site locations and the slope of the terrain at Taiaroa Head—a type of analysis that is commonly used in habitat requirement studies. The second explores the visibility of nest sites with the aim of assessing proposed sites for the installation of video surveillance cameras. The aim of this experiment was to show how the prototype SIS could be used to evaluate proposed management actions in a manner that has no impact on the colony itself. The final experiment explores spatial and temporal relationships that are implicitly present in breeding data by extracting and describing nest dispersal patterns exhibited by the progeny of one Northern royal albatross over five generations. Finally the design and the implementation of the prototype SIS are critically reviewed. It was found that the prototype was subject to two major problems; it did not implement the relational data model according to the system design specification and hard-copy output from analyses were difficult to obtain. These problems arose from the GIS software used to implement the prototype but they are not insurmountable and need not be an issue in an operational implementation. Despite these problems, the prototype SIS did demonstrate that a spatial information system provided significant improvements in the way data are collected, managed, analysed and used in producing useful management information.
2011-04-07T03:12:31ZIncorporating a new computational reasoning approach to spatial modellinghttp://hdl.handle.net/10523/1142
Incorporating a new computational reasoning approach to spatial modelling
1996-12
Holt, Alec
Decision support systems, statistics and expert systems were some of the mainstay techniques used for modelling environmental phenomena. Now modelling systems utilise artificial intelligence (AI) techniques for the extra computational analysis they provide. Whilst operating in a toolbox environment and by adopting AI techniques, the geographic information system (GIS) modellers have greater options available for solving problems. This paper outlines a new approach in applying artificial intelligence techniques to solve spatial problems. The approach combines case-based reasoning (CBR) with geographic information systems and allows both techniques to be applied to solve spatial problems. More specifically this paper examines techniques applied to the problem of soil classification. Spatial cases are defined and analysed using the case-based reasoning techniques of retrieve, reuse, revise and retain. Once the structure of cases are defined a case base is compiled. When the case base is of sufficient size, the problem of soil classification is tested using this new approach. The problem is solved by searching the case base for another spatial phenomena similar to that which exists. Then the knowledge from that searched case is used to formulate an answer to the problem. A comparison of the results obtained by this approach and a traditional method of soil classification is then undertaken. This paper also documents the saving data concept in translating from decision trees to CBR. The logistics of the problems that are characteristic of case-based reasoning systems are discussed, for example, how should the spatial domain of an environmental phenomena be best represented in a case base? What are the constraints of CBR, what data are lost, and what functions are gained? Finally, the following question is posed: “to what real world level can the environment be modelled using GIS and case-based reasoning techniques”?
Part of the GeoComputation '96 Special Issue 96/25; follow the "related link" to download the entire collection as a single document.
2011-04-07T03:06:46ZInvestigating complexities through computational techniqueshttp://hdl.handle.net/10523/1126
Investigating complexities through computational techniques
2000-02
Holt, Alec
This article outlines similarity applied to the general environment and geographical information domains. The hypothesis is if physical and social sciences manifest similar amenities, then similarity would be a generative technique to analyse the cached information inherent in the data retrieved. Similarity is examined concerning the spatial grouping of natural kinds in a complex environment.
2011-04-07T03:06:41ZData sharing using the X.500 directoryhttp://hdl.handle.net/10523/1096
Data sharing using the X.500 directory
1996-12
Pascoe, Richard
Sharing geographical data sets is highly desirable for economical and technical reasons. In this paper the author describes the development of an agency for sharing geographical data which is based on the use of the ISODE implementation of the X.500 Directory Service and a collection of software agents which collaborate with each other to perform the various task associated with sharing data.
Part of the GeoComputation '96 Special Issue 96/25; follow the "related link" to download the entire collection as a single document.
2011-04-07T03:06:31ZDevelopment of a generic system for modelling spatial processeshttp://hdl.handle.net/10523/1071
Development of a generic system for modelling spatial processes
1998-03
Marr, Andrew; Pascoe, Richard; Benwell, George L; Mann, Samuel
In this paper is proposed a structure for the development of a generic graphical system for modelling spatial processes (SMSP). This system seeks to integrate the spatial data handling operations of a GIS with specialist numerical modelling functionality, by the description of the processes involved. A conceptual framework is described, the foundation of which are six defined modules (or services) that are considered a minimum requirement for basic system operation. The services are identified following description of the three key components to systems integration, and the examination of the preferred integrating structure. The relationship of the integration components to sample commentary on the future requirements of integration is discussed, and the benefits and deficiencies of an implemented system for modelling spatial processes are noted.
2011-04-07T03:06:23ZEnvironmental decisions with spatial process modellinghttp://hdl.handle.net/10523/1057
Environmental decisions with spatial process modelling
1996-12
Mann, Samuel
This paper first describes the difficulties inherent in supporting a class of environmental problems, those involved in Regional Environmental Decision Making. A set of conceptual criteria are presented along with discussion on how the criteria might be approached. It is shown that a major obstacle is the need for a system that integrates components of Geographic Information Systems with process modelling functions. A new approach, Spatial Process Modelling is proposed. More detailed design criteria for this system are developed which are then used to develop a prototype system. The system is described and benefits and limitations discussed.
Part of the GeoComputation '96 Special Issue 96/25; follow the "related link" to download the entire collection as a single document.
2011-04-07T03:06:19ZUser defined spatial business rules: storage, management and implementation — a pipe network case studyhttp://hdl.handle.net/10523/1052
User defined spatial business rules: storage, management and implementation — a pipe network case study
1998-03
Cockcroft, Sophie
The application of business rules as a means of ensuring data quality is an accepted approach in information systems development. Rules, defined by the user, are stored and manipulated by a repository or data dictionary. The repository stores the system design, including rules which result from constraints in the user's environment, and enforces these rules at runtime. The work presented here represents the application of this approach to spatial information system design using an integrated spatial software engineering tool (ISSET) with a repository at its core.
Please note that this is a searchable PDF derived via optical character recognition (OCR) from the original source document. As the OCR process is never 100% perfect, there may be some discrepancies between the document image and the underlying text.
2011-04-07T03:06:17Z